U.S. scientists say they’ve determined the human brain responds quickly when a person views erotic images.

Washington University School of Medicine researchers measured the brainwave activity of 264 women as they viewed a series of 55 color slides containing various scenes that included water skiers, snarling dogs and partially-clad couples in sensual poses.

The scientists found when the women viewed erotic pictures, their brains produced stronger and faster electrical responses, suggesting different neural circuits might be involved in the processing of erotic images.

That surprised us, said first author Assistant Professor of Psychiatry Andrey Anokhin. We believed both pleasant and disturbing images would evoke a rapid response, but erotic scenes always elicited the strongest response.

The researchers learned regardless of a picture’s content, the brain acts very quickly, with electrical activity called event-related potentials beginning firing in the brain’s cortex long before a person is conscious of whether they’re seeing a pleasant, unpleasant or neutral picture.

But when the picture is erotic, ERPs begin firing within 160 milliseconds — about 20 percent faster than with any of the other pictures.

The study appeared in the journal Brain Research and is now available online.